The linear amplifier is a key component in many electronic systems. Specifically, linear amplifiers can be implemented in high-speed communication (e.g., fiber optic) networks and systems. For example, in a fiber optic system, a linear amplifier can be used in a fiber optic transmitter to drive input data signals into a laser modulator stage for conversion to modulated (e.g., using pulse-amplitude modulation or PAM) optical signals. In such applications, the linear amplifier is expected to exhibit accurate (e.g., high linearity, low distortion) amplification of the input data signals over a maximum output signal range. Distortion and/or other non-linear characteristics introduced by the linear amplifier can result in an increase in bit-error-rate (BER) and/or other system performance issues. A limited output signal range can further limit the ability of the fiber optic system to implement higher orders of multi-level signaling (e.g., PAM-16 having 16-level signaling) to accommodate the continually increasing demand for more data bandwidth over a fixed transmission medium.
Unfortunately, legacy approaches to implementing linear amplifiers having the foregoing characteristics can be limited at least as pertains to certain performance aspects. For example, one implementation of a linear amplifier can include a differential pair amplifier with degeneration resistors. With this approach, the output signal linearity degrades at increased output values. The degeneration resistor values can be increased to extend the linear output range, but the degeneration resistor value increase will also reduce the gain. The bias current for the differential pair amplifier can be increased to recover the gain, but the bias current increase will increase the power consumption of the linear amplifier. Other legacy approaches to extending the output signal range of a linear amplifier can further increase die area consumption (e.g., of the integrated circuit implementing the linear amplifier) and/or power consumption.
Techniques are therefore needed to address the problem of implementing techniques for extending the output signal range of a linear amplifier that exhibit a minimum increase in die area consumption and power consumption. None of the aforementioned legacy approaches achieve the capabilities of the herein-disclosed techniques for a linear amplifier with extended linear output range. Therefore, there is a need for improvements.